The optical network topology has experienced an isolated node, a linear topology and a ring topology. At present, many networks have been provided with a topology of Mesh or quasi-Mesh Network. An optical Network 10 as shown in FIG. 1 includes a plurality of nodes 11 interconnected by a Mesh topology. The protection switching technique also has developed synchronously with the evolution of networks. ITU recommendations such as G.783, G.841, G.842 and the like provide protection methods applicable for a Link Network and a Ring Network, such as, MSP (Multiplex. Section Protection) 1+1, MSP 1:n, UPSR (Unidirectional Path Switched Ring), BLSR (Bi-directional Line Switching Ring), etc., which have been used wildly.
Although the Mesh Network topology has been used in an optical network system for some time, the protections for a transport plane mainly are a linear protection and a ring protection. The protection for a cross-ring (i.e. a protection ring) service mostly adopts a DNI (Dual-Node Interconnection) method. However, this DNI method relatively wastes resources and also has certain demands on the network structure, that is, a dual-node interconnection is generally required, and the configuration thereof is relatively complicated.
FIG. 2 shows a schematic diagram of a DNI protection with an SNCP (Sub Network Connection Protection), wherein a ring includes nodes 21, 22, 23 and a ring includes nodes 24, 25, 26 are interconnected via a pair of nodes 23, 24 and a pair of nodes 22, 25. According to this solution, each service is adapted to an SNCP service, where a dual-transmission of the service must be performed on an on-ring node and two interconnected nodes of a present ring, and a selective reception of the service can be performed on the two interconnected nodes of another ring and an off-node of the service of another ring. Since in this solution each cross-ring service needs the dual-transmission, a great deal of bandwidth resources may be occupied, and the configuration process may be very complicated. Moreover, this solution may be only applicable for the case of the dual-node interconnection, and fail to provide an effective protection for the case where the rings are interconnected merely via a single node or share no common node.
Also, a method interconnecting rings with the Multiplex Section can provide such a protection. Generally, this method performs a service dual-transmission on interconnected local-ring nodes, and performs a selective reception on interconnected nodes at the same side of another ring. The configuration process for this method may be complicated which requires a manual configuration), and the bandwidth on a Multiplex Section ring may be occupied excessively (in particular when the interconnected nodes are not adjacent ones on the ring). Moreover, this solution may be only applicable for the case of a dual-node interconnection, and fail to provide an effective protection for the case where the rings are interconnected merely via a single node or share no common node.